A two-year-old child from Meghalaya’s West Garo Hills district reportedly tested positive for polio , a highly infectious, debilitating, and possibly fatal viral disease that once afflicted millions but now has largely been consigned to the history books due to the development of an effective vaccine.
What is Vaccine Derived Polio Virus?
-A vaccine-derived poliovirus is a strain related to the weakened version of the live poliovirus contained in the oral polio vaccine (OPV).
-‘Polio drops’ are by and large safe , they have led to the successful eradication of the infection in most countries — but on rare occasions can trigger the disease in children with weak immune systems.
-In some cases, the weakened virus can continue circulating from child to child, gaining back its ability to transmit quickly, and then cause severe infection every time it spreads.
-The virus in the vaccine can also cause chronic infection in children with weakened immune systems, replicating in their gut for years and slowly gaining its ability to cause severe infection. This is what seems to have happened in the Meghalaya case as well.
-India’s last reported case of wild poliovirus (i.e. the infection caused by the naturally occurring version of the virus) was detected in West Bengal’s Howrah district in 2011.
-India was declared polio-free in 2014 after successfully preventing any wild polio infections for three years.
Types of Poliovirus:
-WPV1, WPV2, and WPV3 are three types of wild polioviruses (naturally occurring), with identical symptoms but different genetic structures.
-WPV2 and WPV3 were eradicated in 2015 and 2019 respectively with ongoing global efforts to eradicate WPV1.
-Currently, wild poliovirus is endemic in Pakistan and Afghanistan.
Transmission:
The virus primarily spreads through the fecal-oral route and can multiply in the intestine, where it can invade the nervous system. It predominantly affects children under five.
Vaccines:
Oral Polio Vaccine (OPV): Administered as a birth dose, followed by three primary doses at 6, 10, and 14 weeks, and a booster dose at 16-24 months.
Injectable Polio Vaccine (IPV): This vaccine is given as an additional dose along with the third DPT (Diphtheria, Pertussis, and Tetanus) vaccine under the Universal Immunization Programme (UIP).
Symptoms:
-Initial symptoms are fever, fatigue, headache, vomiting, stiffness of the neck and pain in the limbs.
-The virus multiplies in the intestine and invades the nervous system and can cause total paralysis.
-One in 200 infections leads to irreversible paralysis (usually in the legs).
-Among those paralysed, 5–10% die when their breathing muscles become immobilised.
Preventing the emergence and spread of vaccine-derived poliovirus (VDPV) involves several key strategies:
1. Use of Inactivated Polio Vaccine (IPV):
The shift from Oral Polio Vaccine (OPV) to Inactivated Polio Vaccine (IPV) is a significant step in preventing VDPV. IPV does not contain live virus, so it cannot cause VDPV.
2. High Immunization Coverage:
Ensuring high immunization coverage in communities is essential. This reduces the chances of the weakened virus in OPV spreading and mutating in under-immunized populations.
3. Strong Surveillance Systems:
Robust surveillance systems are necessary to quickly detect and respond to any cases of poliovirus, whether wild or vaccine-derived.
4. Hygiene and Sanitation:
Improving sanitation and hygiene reduces the spread of poliovirus, including VDPV, in environments where the virus might otherwise circulate.
By maintaining high vaccination coverage and moving towards IPV, the risk of VDPV can be significantly minimized, supporting the global effort to eradicate polio.